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Network Working Group                                           A. Malis
Internet-Draft                                               Independent
Intended status: Informational                                   X. Geng
Expires: July 23, 2020                                           M. Chen
                                                                  Huawei
                                                                  F. Qin
                                                            China Mobile
                                                        January 20, 2020


      Deterministic Networking (DetNet) Controller Plane Framework
            draft-malis-detnet-controller-plane-framework-03

Abstract

   This document provides a framework overview for the Deterministic
   Networking (DetNet) controller plane.  It discusses concepts and
   requirements that will be basis for Detnet controller plane solution
   documents.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 23, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  DetNet Controller Plane Requirements  . . . . . . . . . . . .   4
     2.1.  DetNet Control Plane Requirements . . . . . . . . . . . .   4
     2.2.  DetNet Management Plane Requirements  . . . . . . . . . .   5
     2.3.  Requirements For Both Planes  . . . . . . . . . . . . . .   5
   3.  DetNet Control Plane Architecture . . . . . . . . . . . . . .   5
     3.1.  Distributed Control Plane and Signaling Protocols . . . .   6
     3.2.  SDN/Fully Centralized Control Plane . . . . . . . . . . .   7
     3.3.  Hybrid Control Plane  . . . . . . . . . . . . . . . . . .   7
   4.  DetNet Control Plane Additional Details and Issues  . . . . .   8
     4.1.  Explicit Paths  . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  Resource Reservation  . . . . . . . . . . . . . . . . . .   9
     4.3.  PREOF Support . . . . . . . . . . . . . . . . . . . . . .   9
     4.4.  DetNet in a Traditional MPLS Domain . . . . . . . . . . .  10
     4.5.  DetNet in a Traditional IP Domain . . . . . . . . . . . .  11
     4.6.  DetNet in a Segment Routing Domain  . . . . . . . . . . .  11
   5.  Management Plane Overview . . . . . . . . . . . . . . . . . .  11
     5.1.  Provisioning  . . . . . . . . . . . . . . . . . . . . . .  12
     5.2.  DetNet Operations, Administration and Maintenance (OAM) .  12
       5.2.1.  OAM for Performance Monitoring (PM) . . . . . . . . .  12
       5.2.2.  OAM for Fault/Defect Management (FM)  . . . . . . . .  12
   6.  Gap Analysis  . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  13
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     10.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   Deterministic Networking (DetNet) provides the capability to carry
   specified unicast and/or multicast data flows for real-time
   applications with extremely low data loss rates and bounded latency
   within a network domain.  As discussed in the Deterministic
   Networking Architecture [RFC8655], techniques used to provide this
   capability include reserving data plane resources for individual (or
   aggregated) DetNet flows in some or all of the intermediate nodes
   along the path of the flow, providing explicit routes for DetNet
   flows that do not immediately change with the network topology, and



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   distributing data from DetNet flow packets over time and/or space to
   ensure delivery of each packet's data in spite of the loss of a path.

   The DetNet data plane is defined in a set of documents that are
   anchored by the DetNet Data Plane Framework
   [I-D.ietf-detnet-data-plane-framework] and the associated DetNet MPLS
   [I-D.ietf-detnet-mpls] and IP [I-D.ietf-detnet-ip] data plane
   specifications, with additional details and subnet mappings provided
   in [I-D.ietf-detnet-ip-over-mpls],
   [I-D.ietf-detnet-mpls-over-udp-ip], [I-D.ietf-detnet-mpls-over-tsn],
   [I-D.ietf-detnet-ip-over-tsn], and
   [I-D.ietf-detnet-tsn-vpn-over-mpls].

   While the Detnet Architecture and Data Plane Framework documents are
   primarily concerned with data plane operations, they do contain some
   references and requirements for functions that would be required in
   order to automate DetNet service provisioning and monitoring via a
   DetNet controller plane.  The purpose of this document is to gather
   these references and requirements into a single document and discuss
   how various possible DetNet controller plane architectures could be
   used to satisfy these requirements, while not providing the actual
   protocol details for a DetNet controller plane solution.  Such
   controller plane protocol solutions will be the subject of subsequent
   documents.

   Note that in the DetNet overall architecture, the controller plane
   includes what are more traditionally considered separate control and
   management planes.  Traditionally, the management plane is primarily
   involved with node and network provisioning, operational OAM for
   performance monitoring, and troubleshooting network behaviors and
   outages, while the control plane is primarily responsible for the
   instantiation and maintenance of flows, MPLS label allocation and
   distribution, and active in-band or out-of-band signaling to support
   these functions.  In the DetNet architecture, all of this
   functionality is combined into a single Controller Plane.  See
   Section 4.4.2 of [RFC8655] and the aggregation of Control and
   Management planes in [RFC7426] for further details.

1.1.  Terminology

   This document uses the terminology established in the DetNet
   Architecture [RFC8655], and the reader is assumed to be familiar with
   that document and its terminology.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP




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   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  DetNet Controller Plane Requirements

   Other DetNet documents, including [RFC8655] and
   [I-D.ietf-detnet-data-plane-framework], contain requirements for the
   Controller Plane.  For convenience, these requirements have been
   compiled here.  These requirements have been organized to show those
   primarily related to the control plane, those primarily relate to the
   management plane, and those applicable to both planes.

2.1.  DetNet Control Plane Requirements

   The primary requirements of the DetNet Control Plane are that it must
   be able to:

   o  Support the dynamic creation, modification, and deletion of DetNet
      flows.  This may include some or all of explicit path
      determination, link bandwidth reservations, restricting flows to
      IEEE 802.1 Time-Sensitive Networking (TSN) links, node buffer and
      other resource reservations, specification of required queuing
      disciplines along the path, ability to manage bidirectional flows,
      etc., as needed for a flow.

   o  Support DetNet flow aggregation and de-aggregation via the ability
      to dynamically create and delete flow aggregates (FAs), and be
      able to modify existing FAs by adding or deleting participating
      flows.

   o  Allow flow instantiation requests to originate in an end
      application (via an Application Programming Interface (API), via
      static provisioning, or via a dynamic control plane, such as a
      centralized SDN controller or distributed signaling protocols.
      See Section 3 for further discussion of these options.

   o  In the case of the DetNet MPLS data plane, manage DetNet Service
      Label (S-Label), Forwarding Label (F-Label), and Aggregation Label
      (A-Label) [I-D.ietf-detnet-mpls] allocation and distribution.

   o  Also in the case of the DetNet MPLS data plane, support the DetNet
      service sub-layer, which provides DetNet service functions such as
      protection and reordering through the use of packet replication,
      duplicate elimination, and packet ordering functions (PREOF).

   o  Support queue control techniques defined in Section 4.5 of
      [RFC8655] and [I-D.finn-detnet-bounded-latency] that require time
      synchronization among network nodes.



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   o  Advertise static and dynamic node and link resources such as
      capabilities and adjacencies to other network nodes (for dynamic
      signaling approaches) or to network controllers (for centralized
      approaches).

   o  Scale to handle the number of DetNet flows expected in a domain
      (which may require per-flow signaling or provisioning).  This is
      similar to scalability requirements associated with network
      slicing [I-D.dong-spring-sr-for-enhanced-vpn].

   o  Provision flow identification information at each of the nodes
      along the path.  Flow identification may differ depending on the
      location in the network and the DetNet functionality (e.g. transit
      node vs. relay node).

2.2.  DetNet Management Plane Requirements

   The primary requirements of the DetNet Management Plane are that it
   must be able to:

   o  Monitor the performance of DetNet flows and nodes to ensure that
      they are meeting required objectives, both proactively and on-
      demand.

   o  Support DetNet flow continuity check and connectivity verification
      functions.

   o  Support testing and monitoring of packet replication, duplicate
      elimination, and packet ordering functionality in the DetNet
      domain.

2.3.  Requirements For Both Planes

   The following requirements apply to both the DetNet Controller and
   Management Planes:

   o  Operate in a converged network domain that contains both DetNet
      and non-DetNet flows.

   o  Adapt to DetNet domain topology changes such as links or nodes
      failures (fault recovery/restoration).

3.  DetNet Control Plane Architecture

   As noted in the Introduction, the DetNet control plane is responsible
   for the instantiation and maintenance of flows, MPLS label allocation
   and distribution, and active in-band or out-of-band signaling to
   support these functions.



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   The following sections define three possible classes of DetNet
   control plane architectures: a fully distributed control plane
   utilizing dynamic signaling protocols, a fully centralized SDN-like
   control plane, and a hybrid control plane.  They discuss the various
   information exchanges between entities in the network in each of
   these architectures and the advantages and disadvantages of each
   option.

   In each of the following sections, examples are used to illustrate
   possible mechanisms that could be used in each of the architectures.
   These are not meant to be exhaustive or to preclude any other
   possible mechanism that could be used in place of those used in the
   examples.

3.1.  Distributed Control Plane and Signaling Protocols

   In a fully distributed configuration model, User-to-Network Interface
   (UNI) information is transmitted over a (to-be-defined) DetNet UNI
   protocol from the user side to the network side, and then UNI and
   network configuration information propagate in the network via
   distributed control plane signaling protocols.  Using an RSVP-TE
   traffic-engineered MPLS network as an example:

   1.  An IGP collects topology information and DetNet capabilities of
       the network [draft-geng-detnet-info-distribution];

   2.  The control plane of the ingress edge node receives a flow
       establishment request from the UNI and calculates one or more
       valid path(s);

   3.  Using RSVP-TE [RFC3209], the ingress edge node sends a PATH
       message with an explicit route.  After receiving the PATH
       message, the egress edge node sends a RESV message with the
       distributed label and resource reservation request.

   Current reservation-oriented distributed control plane protocols,
   e.g.  RSVP-TE and Stream Reservation Protocol (SRP)
   [IEEE.802.1Qcc-2018], can only reserve bandwidth along the path,
   while the configuration of a fine-grained schedule, e.g., Time Aware
   Shaping (TAS) [IEEE.802.1QBV_2015], is not supported.  If RSVP-TE or
   SRP were to be used for a DetNet application, it would require
   extensions in order to support queue and scheduler reservations in
   addition to bandwidth reservation.

   As discussed in Section 4.9 of [RFC8655], scalability is a primary
   concern for DetNet, given the large number of expected flows in a
   DetNet domain.  This could potentially be much larger than, for
   example, the number of MPLS traffic tunnels in a network using MPLS



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   traffic engineering, which would typically be N*(N-1) tunnels, where
   N is the number of edge routers in the domain.

   Even when flow aggregation is used, DetNet domains can be expected to
   support a very large number of flows that will need particular
   queuing disciplines and/or resource allocation, depending on the
   requirements for each flow.  This could require a large amount of
   dynamic signaling, such as an RSVP-TE session to establish and
   maintain each flow.  Other RSVP-TE scalability concerns are further
   discussed in [RFC5439].

   All of the above tends to argue against a purely distributed control
   plane for DetNet domains.

3.2.  SDN/Fully Centralized Control Plane

   In the fully SDN/centralized configuration model, UNI information is
   transmitted from a Centralized User Configuration or from
   applications via an API or northbound interface to a Centralized
   Controller, which is the sole source of routing and forwarding
   information for the domain.  Configurations of nodes for DetNet flows
   are performed by the controller using a protocol such as NETCONF
   [RFC6241]/YANG [RFC6020] or PCE-CC [RFC8283].  For example:

   1.  A Centralized Controller collects topology information and DetNet
       capabilities of the network via NETCONF/YANG;

   2.  The Controller receives a flow establishment request from a UNI
       and calculates one or more valid path(s) through the network;

   3.  The Controller chooses the optimal path and configures the
       devices along that path for flow transmission via PCE-CC.

3.3.  Hybrid Control Plane

   In the hybrid model, a Controller and control plane protocols work
   together to provide DetNet services, and there are a number of
   possible combinations.  For example:

   1.  A Centralized Controller collects topology information and DetNet
       capabilities of the network via an IGP and/or BGP-LS [RFC7752];

   2.  The Controller receives a flow establishment request from a
       Network Management System and calculates one or more valid
       path(s) through the network;






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   3.  Based on the calculation result, the Controller distributes flow
       path information to the ingress edge node and other information
       (e.g. replication/duplicate elimination) to the relevant nodes.

   4.  Using RSVP-TE, the ingress edge node sends a PATH message with an
       explicit route.  After receiving the PATH message, the egress
       edge node sends a RESV message with the distributed label and
       resource reservation request.

   There are many other variations that could be included in a hybrid
   control plane.  This document cannot discuss all the possible control
   plane mechanisms that could be used in hybrid configuration models.
   Every solution has its own mechanisms and corresponding parameters
   that are required for it to work.

4.  DetNet Control Plane Additional Details and Issues

   This section discusses some additional DetNet control plane details
   and issues.

4.1.  Explicit Paths

   Explicit paths are required in DetNet to provide a stable transport
   service and guarantee that DetNet service is not effected when the
   network topology changes.  The following features are necessary to
   have explicit paths in DetNet:

   o  Path computation: DetNet explicit paths need to meet the SLA
      (Service Level Agreement) requirements and/or resource guarantees
      from the application/client, which include bandwidth, maximum end-
      to-end delay, maximum end-to-end delay variation, maximum loss
      ratio, etc.  In an distributed system with IGP-TE, CSPF
      (Constrained Shortest Path First) can be used to compute a set of
      feasible paths for a DetNet service.  In a system with a network
      controller, a PCE (Path Computation Engine) can compute paths
      satisfying the requirements of DetNet with the network information
      collected from the DetNet domain.

   o  Path establishment: Once the path has been computed, the options
      discussed in Section 3 can be used to establish the path.  Also
      see Section 4.4 for some additional considerations depending on
      the details of the network infrastructure.

   o  Strict or loose paths: An explicit path is strict when every
      intermediate hop is specified so that its route can't change.  An
      explicit path is loose when any IGP route is allowed along the
      path.  Generally, end-to-end SLA guarantees require a strict
      explicit path in DetNet.  However, when the IGP route is known to



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      be able to meet the SLA requirements, loose explicit paths are
      also acceptable.

4.2.  Resource Reservation

   Network congestion could cause uncontrolled delay and/or packet loss.
   DetNet flows are supposed to be protected from congestion, so
   sufficient resource reservation for DetNet service is necessary.
   Resources in the network are complex and hard to quantize, and may
   include such entities as packet processing resources, packet
   buffering, port and link bandwidth, and so on.  The resources a
   particular flow requires are determined by the flow's characteristics
   and SLA.

   o  Resource Allocation: Port bandwidth is one of the basic attributes
      of a network device which is easy to obtain or calculate.  In
      current traffic engineering implementations, network resource
      allocation is synonymous with bandwidth allocation.  A DetNet flow
      is characterized with a traffic specification as defined in
      [I-D.ietf-detnet-flow-information-model], including attributes
      such as Interval, Maximum Packets Per Interval, and Maximum
      Payload Size.  The traffic specification describes the worst case,
      rather than the average case, for the traffic, to ensure that
      sufficient bandwidth and buffering resources are reserved to
      satisfy the traffic specification.

   o  Device configuration with or without flow discrimination: The
      resource allocation can be guaranteed by device configuration.
      For example, an output port bandwidth reservation can be
      configured as a parameter of queue management and the port
      scheduling algorithm.  When DetNet flows are aggregated, a group
      of DetNet flows share the allocated resource in the network
      device.  When the DetNet flows are treated independently, the
      device should maintains a mapping relationship between a DetNet
      flow and its corresponding resources.

4.3.  PREOF Support

   DetNet path redundancy is supported via packet replication, duplicate
   elimination, and packet ordering functions (PREOF).  A DetNet flow is
   replicated and goes through multiple networks paths to avoid packet
   loss caused by device or link failures.  In general, current control
   plane mechanisms that can be used to establish an explicit path,
   whether distributed or centralized, support point-to-point (P2P) and
   point-to-multipoint (P2MP) path establishment.  PREOF requires the
   ability to compute and establish a set of multiple paths (multiple
   LSP segments in an MPLS network) from the point of packet replication
   to the point of packet merging and ordering.  Protocol extensions



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   will be required to support this new feature.  Terminology will also
   be required to refer to this coordinated set of LSP segments, such as
   an "LSP graph".

4.4.  DetNet in a Traditional MPLS Domain

   For the purposes of this document, "traditional MPLS" is defined as
   MPLS without the use of segment routing (see Section 4.6 for a
   discussion of MPLS with segment routing) or MPLS-TP [RFC5960].

   In traditional MPLS domains, a dynamic control plane using
   distributed signaling protocols is typically used for the
   distribution of MPLS labels used for forwarding MPLS packets.  The
   dynamic signaling protocols most commonly used for label distribution
   are LDP [RFC5036], RSVP-TE, and BGP [RFC8277] (which enables BGP/
   MPLS-based Layer 3 VPNs [RFC4384] and Layer 2 VPNs [RFC7432]).

   Any of these protocols could be used to distribute DetNet Service
   Labels (S-Labels) and Aggregation Labels
   (A-Labels)[I-D.ietf-detnet-mpls].  As discussed in
   [I-D.ietf-detnet-data-plane-framework], S-Labels are similar to other
   MPLS service labels, such as pseudowire, L3 VPN, and L2 VPN labels,
   and could be distributed in a similar manner, such as through the use
   of targeted LDP or BGP.  If these were to be used for DetNet, they
   would require extensions to support DetNet-specific features such as
   PREOF, aggregation (A-Labels), node resource allocation, and queue
   placement.

   However, as discussed in Section 3.1, distributed signaling protocols
   may have difficulty meeting DetNet's scalability requirements.  MPLS
   also allows SDN-like centralized label management and distribution as
   an alternative to distributed signaling protocols, using protocols
   such as PCEP and OpenFlow [OPENFLOW].

   PCEP, particularly when used as a part of PCE-CC, is a possible
   candidate protocol to use for centralized management of traditional
   MPLS-based DetNet domains.  However, PCE path calculation algorithms
   would need to be extended to include the location determination for
   PREOF nodes in a path, and the means to signal the necessary resource
   reservation and PREOF function placement information to network
   nodes.  See ((?I-D.ietf-pce-pcep-extension-for-pce-controller)) for
   further discussion of PCE-CC and PCEP for centralized control of an
   MPLS domain.








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4.5.  DetNet in a Traditional IP Domain

   For the purposes of this document, "traditional IP" is defined as IP
   without the use of segment routing (see Section 4.6 for a discussion
   of IP with segment routing).  In a later revision of this document,
   this section will discuss possible protocol extensions to existing IP
   routing protocols such as OSPF, IS-IS, and BGP.  It should be noted
   that a DetNet IP domain is simpler than a DetNet MPLS domain, and
   doesn't support PREOF, so only one path per flow or flow aggregate is
   required.

4.6.  DetNet in a Segment Routing Domain

   Segment Routing [RFC8402] is a scalable approach to building network
   domains that utilizes a combination of source routing in packet
   headers and centralized network control to compute paths through the
   network and distribute those paths with associated policy to network
   edge nodes for use in packet headers.  It reduces the amount of
   network signaling associated with distributed signaling protocols
   such as RSVP-TE, and also reduces the amount of state in core nodes
   compared with that required for traditional MPLS and IP routing, as
   the state is now in the packets rather than in the routers.  This
   could be useful for DetNet, where a very large number of flows
   through a network domain are expected, which would otherwise require
   the instantiation of state for each flow traversing each node in the
   network.

   In a later revision of this document, this section will discuss the
   interactions between DetNet Control and Management planes with
   Segment Routing Control and Management planes, so that DetNet can be
   used in a Segment Routing environment.  Note that the DetNet MPLS and
   IP data planes described in [I-D.ietf-detnet-mpls] and
   [I-D.ietf-detnet-ip] were constructed to be compatible with both
   types of segment routing, SR-MPLS [RFC8660] and SRv6
   [I-D.ietf-6man-segment-routing-header].  However, as of this writing,
   traffic engineering and resource reservation for segment routing are
   currently unsolved problems.

5.  Management Plane Overview

   The Management Plane includes the ability to statically provision
   network nodes and to use OAM to monitor DetNet performance and detect
   outages or other issues at the DetNet layer.








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5.1.  Provisioning

   Static provisioning in a Detnet network will be performed via the use
   of appropriate YANG models, including [I-D.ietf-detnet-yang] and
   [I-D.ietf-detnet-topology-yang].

5.2.  DetNet Operations, Administration and Maintenance (OAM)

   The overall framework and requirements for DetNet OAM are discussed
   in [I-D.mirsky-detnet-oam].  This document currently includes
   additional OAM details that may eventually be merged into that
   document.

5.2.1.  OAM for Performance Monitoring (PM)

5.2.1.1.  Active PM

   Active PM is performed by injecting OAM packets into the network to
   estimate the performance of the network by measuring the performance
   of the OAM packets.  Adding extra traffic can affect the delay and
   throughput performance of the network, and for this reason active PM
   is not recommended for use in operational DetNet domains.  However,
   it is a useful test tool when commissioning a new network.

5.2.1.2.  Passive PM

   Passive PM monitors the actual service traffic in a network domain in
   order to measure its performance without having a detrimental affect
   on the network.  As compared to Active PM, Passive PM is much
   preferred for use in DetNet domains.

   A proposal for DetNet passive performance measurement is contained in
   [I-D.chen-detnet-loss-delay].

5.2.2.  OAM for Fault/Defect Management (FM)

   [I-D.mirsky-detnet-oam] contains requirements for fault/defect
   detection and management in a DetNet domain.

6.  Gap Analysis

   In a later revision of this document, this section will contain a gap
   analysis of existing IETF control and management plane protocols not
   already discussed elsewhere in this document for their ability (or
   inability) to satisfy the requirements in Section 2, and discuss
   possible protocol extensions to existing protocols to fill the gaps,
   if any.




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7.  IANA Considerations

   This document has no actions for IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

8.  Security Considerations

   The overall security considerations of DetNet are discussed in
   [RFC8655] and [I-D.ietf-detnet-security].  For DetNet networks that
   make use of Segment Routing (whether SR-MPLS or SRv6), the security
   considerations in [RFC8402] also apply.

   DetNet networks that make use of a centralized controller plane may
   be threatened by the loss of connectivity (whether accidental or
   malicious) between the central controller and the network nodes, and/
   or the spoofing of control messages from the controller to the
   network nodes.  This is important since such networks depend on
   centralized controllers to calculate flow paths and instantiate flow
   state in the network nodes.  For networks that use both DetNet and
   Segment Routing with a centralized controller, this would also
   include the calculation of SID lists and their installation in edge/
   border routers.

   In both cases, such threats may be mitigated through redundant
   controllers, the use of authentication between the controller(s) and
   the network nodes, and other mechanisms for protection against DOS
   attacks.  A mechanism for supporting one or more alternative central
   controllers and the ability to fail over to such an alternative
   controller will be required.

9.  Acknowledgments

   Thanks to Jim Guichard, Donald Eastlake, and Stewart Bryant for their
   review comments.

10.  References

10.1.  Normative References

   [I-D.ietf-detnet-data-plane-framework]
              Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A.,
              Bryant, S., and J. Korhonen, "DetNet Data Plane
              Framework", draft-ietf-detnet-data-plane-framework-03
              (work in progress), October 2019.





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   [I-D.ietf-detnet-flow-information-model]
              Farkas, J., Varga, B., Cummings, R., Jiang, Y., and D.
              Fedyk, "DetNet Flow Information Model", draft-ietf-detnet-
              flow-information-model-06 (work in progress), October
              2019.

   [I-D.ietf-detnet-ip]
              Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A.,
              Bryant, S., and J. Korhonen, "DetNet Data Plane: IP",
              draft-ietf-detnet-ip-04 (work in progress), November 2019.

   [I-D.ietf-detnet-mpls]
              Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A.,
              Bryant, S., and J. Korhonen, "DetNet Data Plane: MPLS",
              draft-ietf-detnet-mpls-04 (work in progress), November
              2019.

   [I-D.ietf-detnet-security]
              Mizrahi, T., Grossman, E., Hacker, A., Das, S., Dowdell,
              J., Austad, H., and N. Finn, "Deterministic Networking
              (DetNet) Security Considerations", draft-ietf-detnet-
              security-07 (work in progress), January 2020.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC7426]  Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
              Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
              Defined Networking (SDN): Layers and Architecture
              Terminology", RFC 7426, DOI 10.17487/RFC7426, January
              2015, <https://www.rfc-editor.org/info/rfc7426>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,
              <https://www.rfc-editor.org/info/rfc8655>.




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10.2.  Informative References

   [I-D.chen-detnet-loss-delay]
              Chen, M. and A. Malis, "DetNet Packet Loss and Delay
              Performance Measurement", draft-chen-detnet-loss-delay-01
              (work in progress), October 2018.

   [I-D.dong-spring-sr-for-enhanced-vpn]
              Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., and
              Z. Li, "Segment Routing for Resource Partitioned Virtual
              Networks", draft-dong-spring-sr-for-enhanced-vpn-06 (work
              in progress), December 2019.

   [I-D.finn-detnet-bounded-latency]
              Finn, N., Boudec, J., Mohammadpour, E., Zhang, J., Varga,
              B., and J. Farkas, "DetNet Bounded Latency", draft-finn-
              detnet-bounded-latency-04 (work in progress), June 2019.

   [I-D.ietf-6man-segment-routing-header]
              Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", draft-ietf-6man-segment-routing-header-26 (work in
              progress), October 2019.

   [I-D.ietf-detnet-ip-over-mpls]
              Varga, B., Farkas, J., Berger, L., Fedyk, D., Malis, A.,
              Bryant, S., and J. Korhonen, "DetNet Data Plane: IP over
              MPLS", draft-ietf-detnet-ip-over-mpls-04 (work in
              progress), November 2019.

   [I-D.ietf-detnet-ip-over-tsn]
              Varga, B., Farkas, J., Malis, A., and S. Bryant, "DetNet
              Data Plane: IP over IEEE 802.1 Time Sensitive Networking
              (TSN)", draft-ietf-detnet-ip-over-tsn-01 (work in
              progress), October 2019.

   [I-D.ietf-detnet-mpls-over-tsn]
              Varga, B., Farkas, J., Malis, A., and S. Bryant, "DetNet
              Data Plane: MPLS over IEEE 802.1 Time Sensitive Networking
              (TSN)", draft-ietf-detnet-mpls-over-tsn-01 (work in
              progress), October 2019.

   [I-D.ietf-detnet-mpls-over-udp-ip]
              Varga, B., Farkas, J., Berger, L., Malis, A., Bryant, S.,
              and J. Korhonen, "DetNet Data Plane: MPLS over UDP/IP",
              draft-ietf-detnet-mpls-over-udp-ip-04 (work in progress),
              November 2019.




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   [I-D.ietf-detnet-topology-yang]
              Geng, X., Chen, M., Li, Z., and R. Rahman, "Deterministic
              Networking (DetNet) Topology YANG Model", draft-ietf-
              detnet-topology-yang-00 (work in progress), January 2019.

   [I-D.ietf-detnet-tsn-vpn-over-mpls]
              Varga, B., Farkas, J., Malis, A., Bryant, S., and D.
              Fedyk, "DetNet Data Plane: IEEE 802.1 Time Sensitive
              Networking over MPLS", draft-ietf-detnet-tsn-vpn-over-
              mpls-01 (work in progress), October 2019.

   [I-D.ietf-detnet-yang]
              Geng, X., Chen, M., Ryoo, Y., Li, Z., and R. Rahman,
              "Deterministic Networking (DetNet) Configuration YANG
              Model", draft-ietf-detnet-yang-04 (work in progress),
              November 2019.

   [I-D.mirsky-detnet-oam]
              Mirsky, G. and M. Chen, "Operations, Administration and
              Maintenance (OAM) for Deterministic Networks (DetNet)",
              draft-mirsky-detnet-oam-03 (work in progress), May 2019.

   [IEEE.802.1QBV_2015]
              IEEE, "IEEE Standard for Local and metropolitan area
              networks -- Bridges and Bridged Networks - Amendment 25:
              Enhancements for Scheduled Traffic", IEEE 802.1Qbv-2015,
              DOI 10.1109/IEEESTD.2016.7572858, March 2016,
              <http://ieeexplore.ieee.org/servlet/
              opac?punumber=7572858>.

   [IEEE.802.1Qcc-2018]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks -- Bridges and Bridged Networks -- Amendment 31:
              Stream Reservation Protocol (SRP) Enhancements and
              Performance Improvements", IEEE 802.1Qcc-2018,
              DOI 10.1109/ieeestd.2018.8514112, October 2018,
              <http://ieeexplore.ieee.org/servlet/
              opac?punumber=8514110>.

   [OPENFLOW]
              Open Networking Foundation, "OpenFlow Switch
              Specification, Version 1.5.1 (Protocol version 0x06)",
              ONF TS-025, March 2015, <https://www.opennetworking.org/
              wp-content/uploads/2014/10/openflow-switch-v1.5.1.pdf>.







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   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC4384]  Meyer, D., "BGP Communities for Data Collection", BCP 114,
              RFC 4384, DOI 10.17487/RFC4384, February 2006,
              <https://www.rfc-editor.org/info/rfc4384>.

   [RFC5036]  Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
              "LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
              October 2007, <https://www.rfc-editor.org/info/rfc5036>.

   [RFC5439]  Yasukawa, S., Farrel, A., and O. Komolafe, "An Analysis of
              Scaling Issues in MPLS-TE Core Networks", RFC 5439,
              DOI 10.17487/RFC5439, February 2009,
              <https://www.rfc-editor.org/info/rfc5439>.

   [RFC5960]  Frost, D., Ed., Bryant, S., Ed., and M. Bocci, Ed., "MPLS
              Transport Profile Data Plane Architecture", RFC 5960,
              DOI 10.17487/RFC5960, August 2010,
              <https://www.rfc-editor.org/info/rfc5960>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <https://www.rfc-editor.org/info/rfc7432>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC8277]  Rosen, E., "Using BGP to Bind MPLS Labels to Address
              Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
              <https://www.rfc-editor.org/info/rfc8277>.




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   [RFC8283]  Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An
              Architecture for Use of PCE and the PCE Communication
              Protocol (PCEP) in a Network with Central Control",
              RFC 8283, DOI 10.17487/RFC8283, December 2017,
              <https://www.rfc-editor.org/info/rfc8283>.

   [RFC8660]  Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing with the MPLS Data Plane", RFC 8660,
              DOI 10.17487/RFC8660, December 2019,
              <https://www.rfc-editor.org/info/rfc8660>.

Authors' Addresses

   Andrew G. Malis
   Independent

   Email: agmalis@gmail.com


   Xuesong Geng
   Huawei

   Email: gengxuesong@huawei.com


   Mach (Guoyi) Chen
   Huawei

   Email: mach.chen@huawei.com


   Fengwei Qin
   China Mobile

   Email: qinfengwei@chinamobile.com















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